Brandt's bat

GB: Data deficient

England: Data deficient

Scotland: Data deficient

Wales: Data deficient

Global: Least concern

Head & body length: 38mm – 50mm

Forearm length: 31mm – 39mm

Wingspan: 210mm – 240mm

Weight: 4.5g – 9.5g

Colour: Fur dark grey or brown, golden tips on back, greyish underneath. Face and base of ears often pinkish.

Brandt's bat was only recognised as a separate species in 1970 because it is so similar to the whiskered bat. After that, most records, especially those of bats in hibernation, were recorded as Brandt’s/whiskered. Then the discovery of Alcathoe bat in 2001 confused things even more.

These three species are often referred to as the small Myotis group, being in the same genus. All three look and sound very similar. Tiny differences in their teeth, the shape of their tragus (a structure of cartilage inside the outer ear, seen in the photo above) and penis shape may help bat workers to identify them. However, the similarity between the three species makes it very difficult to find out more about their ecology.

Brandt’s bats emerge within half an hour of sunset and probably remain active throughout much of the night. They have a rapid and skilful flight, flying at a medium height and more often within woodland than the whiskered bat. They occasionally pick their prey off foliage and often feed near water.

Brandt’s bats are regularly found in buildings, though colonies are more commonly found in the north and west. They are found in all types of houses including some modern ones, but particularly in older buildings with stone walls and slate roofs. It is a crevice dweller, often roosting until hanging tiles, above soffits, in cavity walls and under ridge tiles.

Droppings frequently accumulate in the roof below the ridge and especially below the favoured roost sites, but not particularly at gable ends or on chimneys. Colonies of Brandt’s bats and whiskered bats may use separate parts of the same roof and may also roost with pipistrelles or long eared bats. They do roost in trees and churches, and have been known to use bat boxes.

In winter, Brandt’s bats are regularly found hibernating in caves and tunnels, almost always in small numbers – it is uncertain where the majority of them hibernate. They often lodge in tight crevices and can be found among clusters of other species. Males may stay at the hibernation sites until well into May.

Brandt's bats mainly feed on moths, other small insects and spiders.

Brandt's bats usually mate in autumn, but has been observed in all winter months. Adult females form maternity colonies in the summer, giving birth to their single young in June or early July. The baby is fed solely on its mother’s milk: by three weeks it can fly and by six weeks it can forage for itself.

Some Brandt's bat females reach sexual maturity at three months (in their first autumn) but the majority do not mate until their second autumn.

A Brandt’s bat was discovered hibernating in Siberia with a metal bat ring (which is engraved with a unique reference number) on its forearm, fitted by researchers 41 years before. This makes it not only the oldest known bat, but also the oldest small mammal ever recorded.

Brandt’s bats echolocate between 33kHz and 89kHz, sounding loudest at 45kHz. Their calls sound like dry clicks (similar to Daubenton’s but not as regular and often slower).

They are sometimes mistaken for pipistrelles but their frequency range is much wider.

Brandt’s bat is thought to be slightly less common and widespread than the whiskered bat. It is found throughout England and Wales and has only recently been recorded in Ireland as well.

They are vulnerable to the effects of modern agricultural practices and decline of woodland, which result in loss of suitable feeding habitats and hollow trees for roosting. Brandt's bats are susceptible to pesticides, especially those used as remedial timber treatment chemicals. Disturbance and vandalism of their hibernation sites (caves and tunnels) is an additional threat.